From: jfbode AT nospam DOT mail DOT earthlink DOT net (John Bode)
Newsgroups: comp.lang.c,comp.os.msdos.djgpp
Subject: Re: Menus and mouse: how to tell what to do?
Date: Mon, 27 Jul 1998 08:16:59 -0500
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In article <35ba510b DOT 361228 AT news DOT unisys DOT com DOT br>, brunobg AT geocities DOT com
(Bruno Barberi Gnecco) wrote:

> I'd like to know if it's possible to create and array of function names. For
> instance, let's say that a menu has 5 options; if I could just detect
what is the
> chosen option (let's say, n), I could use the stored function name at the
position
> n, instead of a long switch. Or maybe, a more clever approach to solve
this menu

It is possible to create an array of function pointers.  If you want to
execute a function based on its name, you'll have to create some kind of a
lookup table.  Here's a quick (untested!) example:

#define MAX_FUNC ... /* max number of functions in table */

/*
** Typedef for function pointer.  Since you don't mention what the functions
** take as parameters or what they return, we'll assume functions taking an
** int and a double argument and returning int.  If you're going to have an
** array of function pointers, all the functions need to have the same 
** prototype.
*/
typedef int (*fptr_t) (int, double);

/*
** Struct definition for lookup table
*/
struct flook {
   char   fname[33]; /* function name (up to 32 chars long) */
   fptr_t fptr;      /* pointer to function */
};

/*
** Define functions here.  Assume they are named f1, f2, f3, etc.
*/
...

int main (void)
{
    /*
    ** Create and initialize lookup table
    */
    struct flook ftable[MAX_FUNC] = {{"f1", f1}, {"f2", f2}, {"f3", f3}, ...};
    int i;
    int x;
    double y;
    char fname[33];
    int  result;
    ...
    /*
    ** Search the lookup table based on name, and execute the indicated function
    ** if found
    */
    for (i = 0; i < MAX_FUNC; i++)
    {
        if (!strcmp (fname, flook[i].fname))
        {
               result = (*(flook[i].fptr)) (x, y);
               break;
        }
    }
}

> problem... Actually, I have the same problem with the mouse. 
> What's the best way to tell the program: 'If you click here, do it', or
'If you
> choose this option, do that'??? To handle the mouse hot-spots, I thought about
> creating a struct like:
> struct mousespot {
>     char minx, maxx, miny, maxy;
>    ?function? // problem here
> }
> and check: if ( cursor < maxx && cursor > minx &&  cursor < maxy &&
cursor > miny
> ), but how to handle the function? Would a pointer to a function work? How to
> declare it?
> 
> "There's never enough time to do all the nothing you want" Bill Watterson 
> Bruno Barberi Gnecco <brunobg AT geocities DOT com> ICQ #1383173 - PGP 5.0i user 
> My other OS is Linux -=- http://graphx.home.ml.org -=- Electric Eng, Poli

-- 
John Bode
one grumpy code monkey

  A Programmer writes code that will run at the end of the day.
  A Software Engineer writes code that will run ten years from now.

To email me directly, remove the 'nospam.' from my address.